Confused about 2.35, 2.40 with a JVC RS55 - AVS Forum
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post #1 of 15 Old 02-12-2012, 12:33 PM - Thread Starter
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I am building a home theater, but I'm really confused about what kind of screen to buy. If anyone would care to chime in, I'd really appreciate it.

I am planning on using a JVC RS55 projector without an anamorphic lens. As far as I understand, the "zoom" feature on the projector can stretch the image.


The room: 19 feet long, 16.5 feet wide, 8.5 feet high, completely dark
Distance to first row of seats: 14 feet
Distance to second row of seats: 18 feet
Screen: I've been looking at the Stewart StudioTek130, which is 120" wide


At this point, I think a screen 120" wide will work (?), but I don't understand what aspect ratio I should select. Several people I've talked to have recommended either 2.35:1, 2.40:1 or 2.41:1.

Questions
1) Which aspect ratio should I choose? Are things likely to change in the future as far as aspect ratios?
2) Do I need to worry about screen gain?

Thanks!
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post #2 of 15 Old 02-13-2012, 02:51 AM
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Quote:
Originally Posted by red45030 View Post

Several people I've talked to have recommended either 2.35:1, 2.40:1 or 2.41:1.

2.39:1 is the proper aspect ratio of CinemaScope for film. In video with an anamorphic lens, that AR tends to be 2.37:1. Given you won't use a lens, then I suggest that you go for the 2.40:1.

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post #3 of 15 Old 02-13-2012, 02:57 AM - Thread Starter
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Thanks for your reply. Given my space constraints, I think I'm going to go with a screen that is 106" wide.

Could you explain why a lot of people seem to be encouraging 2.35:1 instead of 2:40:1?
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post #4 of 15 Old 02-13-2012, 04:29 AM
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Quote:
Originally Posted by red45030 View Post


Could you explain why a lot of people seem to be encouraging 2.35:1 instead of 2:40:1?

As I said, 2.39:1 is the correct aspect ratio and I really think that 2.35:1 (said as 235) became the buzz word to describe Scope. Call it "market rounding" if you will.

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post #5 of 15 Old 02-13-2012, 12:18 PM
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Quote:
Originally Posted by red45030 View Post

Thanks for your reply. Given my space constraints, I think I'm going to go with a screen that is 106" wide.

Could you explain why a lot of people seem to be encouraging 2.35:1 instead of 2:40:1?

When comparing 2.35:1 and 2.40:1 screens of the same width, the 2.35:1 will give you a little more height. If you are width limited, this is a good reason to choose the 2.35:1

To be honest, I think you will find a 106" wide scope screen viewed from 14ft to be a little small. Many people find that with a scope screen they can sit closer and/or use a larger screen than they thought without it feeling overwhelming. This is because the height of the screen tends to be more important determining comfortable viewing. The standard for viewing distance is usually stated as between 2-3 screen heights.

If you can, try reading more in this forum about potential setups before locking in your screen size and viewing distance. For ex. I'm viewing my RS55 on a 125" wide 2.35:1 screen from about 10.5ft away. The immersion is great and nobody has complained about the screen being too big or too close. And with the JVC's e-shift "4k-lite" the PQ holds up amazingly well from my main seating and even closer.

One good strategy is to get the projector first and setup a makeshift screen using a sheet, wall etc. Then you can freely experiment with different image sizes and seating distances.
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post #6 of 15 Old 02-13-2012, 12:43 PM
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Quote:
Originally Posted by CAVX View Post

2.39:1 is the proper aspect ratio of CinemaScope for film. In video with an anamorphic lens, that AR tends to be 2.37:1. Given you won't use a lens, then I suggest that you go for the 2.40:1.

2.37 gives you a little more height right?

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post #7 of 15 Old 02-13-2012, 02:49 PM
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Originally Posted by pokekevin View Post

2.37 gives you a little more height right?

Depends on how you look at it. Technically, 2.37 is not as wide as 2.40.

The number 2.37 is a result of adding a 1.33x HE lens to a 16:9 projector where 1.3333333 x 1.7777777 = 2.3703702 and when rounded becomes 2.37.

Even a 2K D-Cinema projector using the ISCO 1.25x is the same.

2048 / 1080 x 1.25 = 2.3703703

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post #8 of 15 Old 03-12-2012, 02:30 AM
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It's inconsequential. The difference on my 11ft wide screen height-wise is 1".
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post #9 of 15 Old 03-12-2012, 11:04 AM
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Quote:
Originally Posted by red45030 View Post

Could you explain why a lot of people seem to be encouraging 2.35:1 instead of 2:40:1?

2.35:1 was originally the aspect ratio for anamorphic photography. That spec was changed to 2.39 in the early '70s, yet people in the industry continue to call it "2.35:1" out of habit even though it's mathematically incorrect. Even people who try to use the correct number often round up to 2.40:1.

When it comes to home video, it's a total crap shoot whether any particular movie will be transferred at 2.40:1 or mildly cropped to 2.35:1, or anywhere in between. That depends on how the specific telecine machine used for the transfer is calibrated.

Which type of screen you want to install will come down entirely to personal preference. On a 2.35:1 screen, a movie transferred as 2.40:1 will have miniscule letterbox bars. On a 2.40:1 screen, a movie transferred as 2.35:1 will wind up with tiny slivers of picture shaved from the top and bottom when you zoom/scale to fill the width. Realistically, both are within tolerances. It just depends on which bothers you less.

If you're planning to use an anamorphic lens, the processing chips in most projectors that will scale the image for the lens are programmed for output onto a 2.35:1 screen. If you use a 2.40:1 screen, you may get some minor geometric distortion that probably won't be noticeable or distracting.

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post #10 of 15 Old 03-12-2012, 12:07 PM
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Quote:
Originally Posted by Josh Z View Post

2.35:1 was originally the aspect ratio for anamorphic photography. That spec was changed to 2.39 in the early '70s, yet people in the industry continue to call it "2.35:1" out of habit even though it's mathematically incorrect. Even people who try to use the correct number often round up to 2.40:1.

When it comes to home video, it's a total crap shoot whether any particular movie will be transferred at 2.40:1 or mildly cropped to 2.35:1, or anywhere in between. That depends on how the specific telecine machine used for the transfer is calibrated.

Which type of screen you want to install will come down entirely to personal preference. On a 2.35:1 screen, a movie transferred as 2.40:1 will have miniscule letterbox bars. On a 2.40:1 screen, a movie transferred as 2.35:1 will wind up with tiny slivers of picture shaved from the top and bottom when you zoom/scale to fill the width. Realistically, both are within tolerances. It just depends on which bothers you less.

If you're planning to use an anamorphic lens, the processing chips in most projectors that will scale the image for the lens are programmed for output onto a 2.35:1 screen. If you use a 2.40:1 screen, you may get some minor geometric distortion that probably won't be noticeable or distracting.

So then, are you saying that it is better to pick a 2.35:1 screen vs. 2.39:1 (or 2.40:1)? I ask because I plan on building a DIY 2.35:1 screen and want to make sure I get the most out of my viewing.
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post #11 of 15 Old 03-12-2012, 03:45 PM
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Originally Posted by psalm234 View Post

So then, are you saying that it is better to pick a 2.35:1 screen vs. 2.39:1 (or 2.40:1)? I ask because I plan on building a DIY 2.35:1 screen and want to make sure I get the most out of my viewing.

My screen is 2.37:1. Because it is curved, it equates to a 2.40:1 flat screen because there is a slight optical compression happening (which is why I have no Grid Distortion). After the A-Lens is calibrated, there are small side pillars like there would be on the said 2.40:1 flat screen. I trim the image so that I am framed flush top to bottom. I do think about these side slivers and applying a small amount of zoom to fill them, but would rather the image is vertically framed with no major light spill than horizontally framed with vertical light spill. Does that make sense?

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post #12 of 15 Old 03-13-2012, 12:27 PM
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Quote:
Originally Posted by CAVX View Post

My screen is 2.37:1. Because it is curved, it equates to a 2.40:1 flat screen because there is a slight optical compression happening (which is why I have no Grid Distortion). After the A-Lens is calibrated, there are small side pillars like there would be on the said 2.40:1 flat screen. I trim the image so that I am framed flush top to bottom. I do think about these side slivers and applying a small amount of zoom to fill them, but would rather the image is vertically framed with no major light spill than horizontally framed with vertical light spill. Does that make sense?

Makes complete sense. That's my reason for going with a 2.40:1 screen. For the vast majority of movies, I will be able to fill my screen top to bottom. For the 2.35 or 2.37 movies, I'd rather have tiny side pillars, rather than letterboxing 2.40 movies on a 2.35 screen. With such a wide screen, I think I'll hardly notice the tiny side pillars. I'm sure I would notice letterboxing all the way across the top and/or bottom of the screen. I should know soon enough though, because my screen arrived the other day. Just need to finish up the theater room and get everything set up. Another month, maybe two, surely by the end of summer.

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post #13 of 15 Old 03-13-2012, 01:39 PM
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Originally Posted by willscam View Post

Makes complete sense. That's my reason for going with a 2.40:1 screen. For the vast majority of movies, I will be able to fill my screen top to bottom. For the 2.35 or 2.37 movies, I'd rather have tiny side pillars, rather than letterboxing 2.40 movies on a 2.35 screen. With such a wide screen, I think I'll hardly notice the tiny side pillars. I'm sure I would notice letterboxing all the way across the top and/or bottom of the screen. I should know soon enough though, because my screen arrived the other day. Just need to finish up the theater room and get everything set up. Another month, maybe two, surely by the end of summer.

Not to discount the decision you've made (which is perfectly valid), but another option for a 2.35:1 screen is simply to zoom up 2.40:1 transfers to fill the height and let a tiny sliver of picture on each side spill over into masking.

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post #14 of 15 Old 03-13-2012, 05:04 PM
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^^^
True that... and the black velvet border on my Screen Excellence frame looks like it would completely soak up any and all light spillover.

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post #15 of 15 Old 03-24-2012, 11:08 PM
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I went 2:37:1 and does a good job with 2:35:1 and 2:40:1.

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